The long-term objectives of this application are to: (1) pursue our preliminary findings that the molecular determinants for regulation of calcitonin (CT) gene expression may differ between human neoplasms arising from thyroid G-cells and those arising from cells in the lung (so-called "ectopic" CT production), and (2) determine, in a transgenic mouse model, the tissue distribution and differentiation sequences of cells transcribing the CT gene, with special emphasis on dissecting lineage relationships between pulmonary endocrine cells and phenotypes of lung cancer. In a human cell culture model consisting of a medullary thyroid carcinoma (MTC) line, a CT-producing lung carcinoma line as well as several non CT producing tumor lines, we will (1) determine whether previously characterized structural features of the CT gene (methylation, chromatin configuration) correlate with its transcriptional activity, (2) pursue , in a transient system using plasmid constructs containing a reporter gene under control of the 5' flanking region of the CT gene, our initial data which suggest that different DNA sequences mediate basal and induced CT gene, expression in MTC and lung carcinoma cells, (3) characterize in each cell type, by gel electrophoresis "shift-up" and DNAase I protection assays, nuclear proteins by DNA-affinity chromatography. We will examine cell-specific and developmental patterns of CT gene expression in transgenic mice by mapping the expression of a reporter gene under control of the transcriptional regularity elements of CT gene. We will also express in these CT-producing cells, selected oncogenes which we have previously shown to alter the differentiation status of CT-producing tumors in vitro. Such studies may allow us to understand the molecular events involved in the pathophysiology of two important CT-producing neoplasms in man, MTC and lung carcinoma They may offer unique opportunity to induce tumor differentiation in vivo, and eventually have clinical relevance to MTC patient and/or to patients suffering form paraneoplastic endocrine syndromes due to ectopic hormone production.